What it means
The ECM detects a circuit intermittent/erratic fault on the hybrid/ev battery pack coolant temperature sensor c circuit. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Sensor C provides a changing coolant-temperature signal for the hybrid or EV battery pack. The module monitors that signal for stability; this code sets when it drops out or jumps erratically, often as a loose connection or weak ground changes with vibration or temperature.
Common causes
Most likely first.
- Sensor connector not seated
- Noisy ground reference
- Connector with intermittent contact under vibration
Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
How to diagnose it
- Review freeze-frame data and scan-tool history, then watch sensor C live data for sudden jumps or dropouts.
- Inspect sensor C's connector seating, terminal tension, harness routing, and ground reference for movement-related faults.
- With the vehicle made safe under its high-voltage procedure, gently move the accessible harness while monitoring the reading for interruption.
- Check the sensor C ground and signal connections for unstable contact using the manufacturer's test procedure.
- If wiring remains stable, test sensor C through temperature changes to identify an intermittent sensor element.
Common fixes
- Reseat and secure the sensor C connector.
- Repair loose, corroded, or damaged terminals and restore a sound ground reference.
- Repair or replace harness sections that lose contact during movement.
- Replace sensor C if its output remains erratic with a sound circuit.
Can I keep driving?
If the warning appears intermittently or the vehicle unexpectedly reduces power or charging, avoid relying on it for a long journey. An intermittent reading can cause the system to restrict battery operation without warning.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.